This invention relates to pressure change indicators and, more particularly, to pressure change indicators of the type suitable for indicating that the pressure in a pneumatic tire has decreased below a predetermined desired level.
In providing a tire pressure level indicator it is known to utilize a pressure-responsive member such as a diaphragm preloaded or biased to move only when the pressure level in the tire drops below the predetermined desired level. Movement of such pressure responsive means has been previously utilized to actuate a pivotal latch for releasing an indicator preloaded for movement and which moves to a position indicating loss of tire pressure below the desired level. One such device is described in U.S. Pat. No. 3,800,736 in which the pressure responsive means is preloaded by the pressure in a reference chamber which is pressurized at a level at or above the predetermined desired tire pressure upon proper inflation of the tire. The aforementioned patented device also utilizes the pressure in the tire to bias the indicator means for movement upon release of same by the latch means.
However, it has been found that the construction of the above-mentioned known tire pressure indicator results in a rather complicated and costly latch arrangement which renders the device difficult to manufacture and maintain in proper working order.